With the explosion of internet usage, including cloud computing, in recent years, data centers have proliferated all over the world, and have brought with them enormous demand for electricity. A recent report in the New York Times (Sep. 22, 2012) after a year-long investigation quotes a designer of hundreds of data centers: “It's staggering for most people, even people in the industry, to understand the numbers, the sheer size of these systems. A single data center can take more power than a medium-size town.”
Industry experts told the Times that all data centers in the world taken together probably consume around 30 billion watts of electricity—approximately the output of 30 nuclear power plants—with data centers in the U.S. consuming one fourth to one third of that. In 2010, U.S. data centers used approximately 76 billion kilowatt-hours, approximately 2 percent of all electricity used in the U.S.
The Times report cites an estimate by EMC and the International Data Corporation “that more than 1.8 trillion gigabytes of digital information were created globally last year.” About three quarters of that was created by ordinary consumers doing what now are ordinary things on the internet (such as sending emails with attached videos), with little thought given to how much infrastructure and energy these uses take up.
This explosion of data shows no signs of slowing down, or even leveling off. For just one example, Facebook announced that it had reached one billion active users on Sep. 14, 2012 (http://newsroom.fb.com/download-media/4227). The New York Times report further quotes a former utility executive now consulting for the power and IT industries: “It's just not sustainable. They're going to hit a brick wall.”
Industry attempts to deal with exploding power demands by data centers have given rise to the metric Power Usage Efficiency, or PUE. This is a data center's total power consumption (numerator) divided by the power actually running the electronics (denominator). A data center with a PUE of 1.7, for example, which is typical for a recently-built facility, would consume 1.7 megawatts of electricity in order to furnish 1 megawatt to the electronics doing the computing work. The additional 0.7 megawatts, or 700 kilowatts, represents overhead.
A sizeable fraction of this overhead is devoted to cooling the electronics. The typical state of the art is to use air cooling, with ambient air, pre-cooled with air conditioning equipment if need be, blown over and through the servers with electric powered fans. Some work has been done using liquid cooling of key individual electronic components, usually processors, but the remainder is still air-cooled.
For the foregoing reasons, there is a need for systems increasing the efficiency with which data centers use electrical power.